Tax-supported debt for U.S. states rose to a net $510 billion in 2011 from $497 billion in 2010, according to Moody’s Investors Service.

The year-over-year increase of 2.5 percent is down from an annual rate as high as 10 percent in the previous two years, the New York-based company said Tuesday in a report.

The rate for 2012 will be “comparable or slightly higher than 2011 levels, but well below the large increases of 2009 and 2010,” according to the statement.